Re: Is VFP or Neon supported in kernel-side code? <EOM>

Hi Tixy,

In general, you cannot use any FP code in the kernel, and there are few exceptions to that. I'm not sure about Neon here, but in general, you have to save the FP registers of the user process and enable the FPU using kernel_fpu_begin() or enable_kernel_fp() and release the FPU context using kernel_fpu_end() or disable_kernel_fp() depending on the architecture, before returning to user space.

I could not find these functions for ARM, maybe they have yet another name. If they don't exist, you might have to add them. In either way, saving the FPU state is generally expensive, so it's worth it only if we use many FP operations at once.

Arnd